Data Analysis

Here is a collection of resources that will help you get started analyzing your NACC datafile.
  • The NACC Handbook offers an overview of the data and some advice for selecting cohorts.
  • The Researchers Data Dictionary will help you understand the variables in the dataset.
  • The Coding Guide is the guidance given to Clinicians collecting the data for each form and question.
Before you send your questions to NACC, check the Frequently Asked Questions below to see If someone has already asked that question.
Finally, review the Checklist for Authors for guidance on transforming your analysis into a publication while adhering to the Data Use Agreement with NACC.
  • Nacc Handbook: Researchers Guide
    This guide will help you to better understand the NACC longitudinal dataset.
  • Researchers Data Dictionary
    For the UDSv3, which is intended as the first and primary resource for those analyzing NACC clinical and demographic data.
  • Coding Guides
    The coding guidebooks provide detailed, annotated explanations of each form on an item-level basis, with instructions, operational definitions, and references. Check here If you are looking for more information about how data is collected in the clinic.
  • Query System
    You can explore the UDS using the Query System to determine if NACC has a large enough sample size to address your research Question.
  • Checklist for Authors
    As you are preparing your data analysis for publication, follow the guidelines in the checklist for Authors.
  • More about using Imaging data: MRI and PET

    Magnetic resonance imaging, along with volumetric summary measures, are available for a subset of participants in the Uniform Data Set. NACC’s MRIs are most appropriately described as a convenience sample of images, voluntarily submitted by several Alzheimer's Disease Research Centers. Imaging data collection and acquisition protocols vary by ADRC; thus, packages of MRI files at NACC may include T1-weighted, FLAIR, DTI, T2, or other MR series (and any combination thereof), and subjects may or may not have multiple scan sessions in the NACC database.

    • For an estimate of the number of available scans that meet your image-type and subject criteria, use NACC’s MRI Preview System.
    • To acquire images and volume data, submit a data request. Both DICOM and NIfTI formats are available. MRIs archived by subject ID and MRI date (.zip), delivered via a cloud-based distribution system and linked to any requested UDS, FTLD, or NP data.
    Image acquisition period2005 – present
    SubjectsADRC subjects enrolled in the Uniform Data Set (UDS)
    Clinical diagnosesNormal cognition, MCI, dementia
    Linked genotype dataAvailable from ADGC and NIAGADS
    Longitudinal MRIsAvailable for some subjects

    NACC is also acquiring amyloid PET images and making them available as DICOM files via data request.

Top FAQ on Data Files and the UDS

  • My data download link has expired – can you send me a new one?
    Download links expire after two weeks. If you need to download data after this time, please send an email to consnacc@uw.edu with your data request # to request an updated link.
  • Does my collaborator need to sign the data use agreement (DUA)? I have new collaborators / I’m no longer working with a collaborator – what needs to be done regarding the DUA?
    All collaborators are bound by the terms of the data use agreement, so you can freely share the data with collaborators on your analysis. You do not need to notify NACC of changes in your collaborators. If your collaborator is preparing the manuscript for this analysis, they should refer to the Checklist of Authors. If you wish to share the data with someone who will not be directly collaborating on your analysis, they will need to submit a new request and separately sign the DUA.
  • How can I get an update to a data file from a previous request?
    Please submit a data request through our website and indicate that you are requesting an update, with the data request # or file name of the previous request.
  • Can you provide a sample size estimate for my analysis before I request data?
    NACC no longer provides sample size estimates for investigators. You can use the Query System to explore the sample size for simple criteria. You can also request the Quick-Access dataset through the Data Request System to explore the dataset in more detail.
  • Why does my proposal and/or publication not appear on the Ongoing & Completed Research page on NACC’s website?
    This page is currently under construction. Please check back later.
  • How was a variable (e.g. Alzheimer’s disease clinical diagnosis) defined?

    In addition to the Researcher’s Data Dictionaries (RDDs), please refer to the data collection forms and coding guidebooks for each dataset for more information on variable definitions. In particular, the coding guidebooks provide detailed, annotated explanations of each form on an item-level basis, with instructions, operational definitions, and references. RDDs, forms, and coding guidebooks can be found on the NACC website:

  • Do I need to submit my dissertation for administrative review?
    You only need to submit manuscripts for review before they are submitted to a journal. Please only submit any part of your thesis that is prepared for manuscript submission.
  • I need a specific imaging type for my study. What does NACC’s imaging database include?

    Magnetic resonance imaging (MRI), along with volumetric summary measures, are available for a subset of participants in the Uniform Data Set. NACC’s MRIs are most appropriately described as a convenience sample of images, voluntarily submitted by ADRCs. Imaging data collection and acquisition protocols vary by ADRC; thus, packages of MRI files at NACC may include T1-weighted, FLAIR, DTI, T2, or other MR series (and any combination thereof), and subjects may or may not have multiple scan sessions in the NACC database. Currently, we are unable to separate packages of MRI files into sequence types. For an estimate of the number of available scans that meet your image-type and subject criteria, use NACC’s MRI Preview System.

    Amyloid PET scans are also available for a small subset of participants.

    Some examples of data that are not available include: function MRI (fMRI), Magnetic Resonance Spectroscopy (MRS), Arterial spin labeling (ASL), FDG-PET, and tau PET scans.

  • Can you provide the predefined cutoff values for CSF biomarkers, or the assays used at each center?
    The CSF biomarker values can vary by assay method (ELISA, Luminex, etc.) and Center. Centers use different lab assay kits which provide ranges for amyloid beta and tau that are scaled completely differently for each brand of kit and have different range and cut off values for positivity. Unfortunately, we do not currently have information on the assay kits used or the cutoff values, so we strongly caution using the data for analysis.
  • I would like to use NACC’s forms in my research study outside of the ADRC program. How can I obtain permission for this?
    Please complete the permission request form and email to naccmail@uw.edu.
  • There are some variables missing from my Quick Access File. Where can I find them?
    All of the variables in the Researchers Data Dictionary (RDD) (excluding CLS, and Z1X) are included in the Quick Access Files.
  • I want to determine if NACC UDS participants overlap with the ADNI cohort, DIAN study, or NIFD/FTLDNI. Can you provide me with participants lists that overlap?
    No, we do not have any information about overlapping participants with these studies.
  • When/how should the COVID forms be collected?
    The collection of the current COVID impact survey is up to the discretion of the ADRCs, since it is not tied to a UDS visit. That said, we encourage you to collect this information at least annually.
  • I am part of an ADRC NP Core and was given a list of NACCIDs from a NACC tissue request. How do I map to PTID?
    Log into the UDS submission system (can also be reached by entering the NACC portal and clicking to “Submit UDS, FTLD, & LBD”). Under “DOWNLOAD DATA,” select the last link, “PTID to NACCID Map.”

If you’re unable to find what you’re looking for, please don’t hesitate to contact us.

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NACC is funded by the National Institute on Aging (U24 AG072122) and located in the Department of Epidemiology at the University of Washington School of Public Health, Walter A. Kukull, Ph.D., Director. © 2022 University of Washington